The overall focus of the Center for Child Environmental Health Risk Research is on mechanisms that define children's susceptibility to pesticides. The Genetic Susceptibility Core will examine differences in genetics (PON1) which affect metabolism and define susceptibility. The functional consequences of these will be assessed in the Neurobehavioral Assessment Facility Core. These studies will be performed in close collaboration with the Molecular Mechanisms Study, which will specifically evaluate the molecular and cellular mechanisms through which pesticides can exert their neurodevelopmental toxicity. In total, these 3 laboratory based studies provide an optimal mix of in vivo and in vitro assessments and molecular, cellular, and genetic evaluations. The Genetic Susceptibility Project will provide information on inter and intraindividual variability for risk characterization modeling by the Risk Characterization Core. Information from the Exposure Assessment Facility Core will ensure that these quantitative assessments are realistic.